Add loose foreign keys (LFK) for p_duo_workflows_checkpoints

Summary

Add loose foreign key (LFK) constraints for all three foreign key relationships on p_duo_workflows_checkpoints:

• namespace_id → namespaces
• project_id → projects
• workflow_id → duo_workflows_workflows

Context

This is a follow-up task from #560503 (closed), which addresses recurring lock contention caused by foreign key constraints on partitions of p_duo_workflows_checkpoints.

After dropping the regular foreign key constraints, we need to implement loose foreign keys to maintain referential integrity without the locking issues. Loose foreign keys provide eventual consistency through async cleanup rather than synchronous constraint enforcement.

Implementation

Follow the guidance in the loose foreign keys documentation to add the three relationships to the LFK YAML configuration.

Related

• Parent issue: #560503 (closed)
• Previous work: !207591 (merged) (dropped FK to namespaces and projects)